Sedum alfredii Shows Superior Light Tolerance over Sedum plumbizincicola with Insights from Multi-Omics Analysis of Lipid and Transcriptomic Responses

The heavy metal hyperaccumulating plant Sedum is limited in its promoted application due to its sensitivity to strong light in summer. This study compared the physiological and molecular differences between Sedum alfredii (SA) and Sedum plumbizincicola (SP), which two species are relatively resistant and not resistant to strong light, respectively, under various light intensities, ranging from 600 to 1400 umol m-2 s-1. Results showed SP exhibited greater susceptibility to strong light induced damage, with complete mortality observed at 1400 umol m-2 s-1 after 6 days, while SA demonstrated significantly higher survival rate, showing minimal to moderate mortality under the same condition. Comparative physiological analysis indicated that SA maintained higher Rubisco activity in leaves and exhibited lower levels of membrane damage under strong light stress compared to SP. Lipidomics analysis identified significant high accumulations of lipids, including ceramides and glycerophospholipids, in SA, which contributed to membrane stabilization. Transcriptomic analysis revealed 6,501 differentially expressed genes (DEGs) shared between the species under strong light intensities, while 977 DEGs were specific to SA. Key processes such as chloroplast function, protein phosphorylation, and defense responses were implicated in SA's superior strong light stress resilience. Weighted gene co-expression network analysis (WGCNA) identified three significant modules, with the MEturquoise module strongly associated with lipid metabolism and stress response pathways. Additionally, SA exhibited a sharp increase in DEGs at 1200/1400 umol m-2 s-1, suggesting the activation of unique protective mechanisms involving microtubule reorganization, cytokinin signaling, and circadian regulation.